Antigen recognition by T lymphocytes

I. Interference with antigen recognition. Muromonab CDS is a monoclonal antibody directed against mouse CD-3 that blocks antigen recognition by T-lymphocytes (use in graft rejection). 

The major histocompatibility complex (MHC) is part of the system that codes for molecules important in immune recognition, including graft rejection. MHC class I and II molecules present antigen fragments to T-lymphocytes. For example, class I molecules bind viral proteins and present them to the CD8+ T cells. Exogenous antigens such as proteins taken into the cell by endocytosis are processed within the cell and presented to CD4+ cells. 

LPS can be directly mitogenic for T cells [130], but the antitumoral activity of lymphocytes depends on antigen recognition by their TCR in the context of the major histocompatibility complex (MHC) class I or n. Though LPS enhance it, T lymphocyte activity requires APC [131]. The effect of LPS on T lymphocytes has been shown to depend on monocytes independent of MHC, but to be due to the secretion of costimulatory signals and IL-12 in humans [132]. In vivo, LPS induces principally the proliferation of CD8+ T lymphocytes, but also that of CD4+ T and B lymphocytes through the activation of APC and secretion of IFN 0(7(3 in C57BL/6 mice [133],... 

Townsend A, Bodmer H (1989) Antigen recognition by class I-restricted T lymphocytes, Ann Rev Immunol 7 601-624. 

Fig. 1. The MHC class II antigen presentation pathway. MHC class II proteins (DR-ot and DR-P) are inserted into the ER membrane and assemble with the invariant chain (li). li blocks the peptide binding groove of DR-ot/p. These complexes are transported to the Golgi apparatus and then directed to TGN/ endosomes by li. There is proteolysis of li, and DR oi/p CLIP complexes arrive in the MIIC. Antigenic proteins are taken up by endocytosis or phagocytosis into endosomes and degraded into peptides, which are also delivered to the MIIC. Peptides are loaded onto DR-oe/p complexes by the action of DM, which binds to class II complexes and exchanges peptides for CLIP. Peptide-loaded class II complexes are transported to the cell surface for recognition by T cell receptors of CD4" T lymphocytes...

KABELITZ D, GLATZEL A, WESCH D (2000), Antigen recognition by human gammadelta T lymphocytes , IntArch Allergy Immunol, 122,1-7. 

Bom, W., Hall, L, Dallas, A., Boymel, J., Shinnick, T., Young, D., Brennan, P O Brien, R. (1990). Recognition of a peptide antigen by heat shock-reactive gamma delta T lymphocytes. Science 249, 67-69. 

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